Various types of swing mechanisms for earthmoving apparatus, including backhoes, cranes, derricks and the like, have been commercially available for many years and numerous of such mechanisms have been disclosed in the prior art for many years. Not only is the mechanical operating efficiency of such mechanism of importance, but also of concern is the configuration and relative size, since it is vital that the center of balance of the backhoe be as close as possible to the hauling tractor to which it is coupled. Thus the smaller the longitudinal displacement between the tractor hitch and the backhoe turret or boom support frame, the more advantageous the arrangement. Where the configuration is held to a minimum, improved tractor balance and stability both longitudinally and laterally results. The trend today has been toward the adaptation of large backhoes on small tractors and when this is done substantial counterweighting may be required. Such counterweight would be added to the end of the tractor opposite the end which is hitched to the backhoe and whenever a counterweight is added increased tractor cost is a direct result. Additionally, counterweighting adds an unnecessary load to the tractor and causes higher fuel consumption as well as reduced operating efficiency and poorer maneuverability. For example, where substantial counterweighting is added to the tractor, it will be more likely to bog down in poor soil condition areas.
Applicant's earlier U.S. Pat. No. 3,894,641, granted July 15, 1975, disclosed one type of swing mechanism which provided a partial solution to these problems.
It is the principal object of this invention to provide an improved swing mechanism for the turret and boom of earthmoving equipment which substantially eliminates the above described difficulties and provides a mechanism of compact configuration.
It is a further object of this invention to provide a swing mechanism of the above type in which the rotational velocity of the boom throughout a horizontal arc of movement versus the linear velocity of the piston rods of the said rams is maintained at a predetermined ratio.
It is another object of this invention to provide a swing mechanism of the above type in which the boom of the earthmoving apparatus is driven with equal power in both directions throughout a horizontal arc of movement.
A further object of this invention is to provide a swing mechanism in which maximum hydraulic force is utilized in both driving directions throughout the boom's horizontal arc of movement.